2. The Circulatory System Created by: Katlin & Morgan

3. Sponges Sponges do not have a true circulatory system. A water flow system performs this function for it instead.

4. Earthworms The earthworm has two main blood vessels – the dorsal and ventral, which carry blood toward either the head or the tail. The dorsal vessel moves the blood towards the head and the ventral vessel moves the blood to the tail. Near the head there are five secondary vessels that serve as the worms “hearts” because they connect the dorsal and ventral vessels. The worm has the simplest closed circulatory system. This means that the blood is confined to vessels, arteries, organs, etc.

5. Frogs The frog has a closed circulatory system with a three chamber heart being the center of the system. Blood with oxygen in it goes into the heart and through the heart’s various processes, oxygen laden blood is forced to all of the cells needing its nutrients. The oxygen poor blood leaves the heart in a series of arteries which lead it to the lungs to be provided with oxygen. Before either of those steps occur, the oxygen rich and oxygen poor blood mix in the heart before being separated again. The frog’s circulatory system is very similar to humans, except they have a three chamber heart which allows the mixing of blood to occur. Humans have a four chamber heart which does not allow this.

6. Humans Humans have a closed circulatory system which uses blood to transport nutrients, wastes, carbon dioxide, oxygen and hormones. The human heart uses a two pump system. One of the pumps is used to send the oxygen poor blood to the lungs and the other pump is used to send oxygen rich blood throughout the body. A system of blood vessels sends the blood to all the parts of the body. Veins carry oxygen poor blood towards the heart and arteries carry oxygen rich blood around the body.

7. The End!